Leaf trait co-variation, response and effect in a chronosequence

Question: Is there any generality in terms of leaf trait correlations and the multiple role of leaf traits (response to and/or effect on) during secondary succession? Location: A secondary successional sere was sampled at four different ages since abandonment from several years to nearly 150 years on the Loess Plateau of northwestern China. Method: Specific leaf area (SLA), leaf mass per area (LMA), leaf nitrogen (Nmass, Narea), leaf phosphorus (Pmass' Parea) and leaf dry matter content (LDMC) were measured for all species recorded in the successional sere. Above-ground net primary productivity (ANPP) and specific rate of litter mass loss (SRLML) were measured as surrogates for ecosystem properties. Soil total carbon (C) and nitrogen (N) were measured in each stage. Leaf traits were related to ecosystem properties and soil nutrient gradients, respectively. Results: LMAis correlated with Narea and Parea, and negatively with Nmass. Correlation between Naea and Parea was higher than between Nmass and Pmass. At the community level, field age, community hierarchy and their interaction explain 64.4 93.5% of the variation in leaf traits. At the species level, field age explains 22.4 45.5% of the variation in leaf traits (excl. Parea) while plant functional group has a significant effect only for Nmass. LDMC is correlated with ANPP and negatively with SRLML; Pmass is correlated with SRLML. Conclusions: Mean values of LMA, N massand N areaare close to the worldwide means, suggesting that large-scale climate has a profound effect on leaf mass and leaf nitrogen allocation, while environmental gradients represented by succession have little influence on leaf-trait values. Correlations between leaf traits, such as LMA-Narea, LMA-Parea and LMA-Nmass shown in previous studies, are confirmed here. Although none of the leaf traits is proved to be both a response trait and an effect trait independent of time scale and community hierarchy, mass-based leaf N is likely a sensitive response trait to soil C and N gradients. In addition, LDMC can be a marker for ANPP and SRLML, while mass-based leaf P can be a marker for SRLML.